134 lines
6.5 KiB
HTML
134 lines
6.5 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>difftime</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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</head>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_chrono_difftime skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading">difftime</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-chrono.html">chrono</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<table class="t-dcl-begin">
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<tbody>
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<tr class="t-dsc-header">
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<td>
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<div>定义于头文件 <code><time.h></code></div>
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</td>
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<td></td>
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<td></td>
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</tr>
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<tr class="t-dcl">
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<td class="t-dcl-nopad">
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<div><span class="mw-geshi c source-c"><span class="kw4">double</span> difftime<span class="br0">(</span> <a href="c-chrono-time_t.html"><span class="kw523">time_t</span></a> time_end, <a href="c-chrono-time_t.html"><span class="kw523">time_t</span></a> time_beg <span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td class="t-dcl-nopad"></td>
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</tr>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</tr>
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</tbody>
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</table>
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<p>以秒数计算二个作为 <span class="t-lc"><a href="c-chrono-time_t.html">time_t</a></span> 对象的日历时间的差（ <span class="t-c"><span class="mw-geshi c source-c">time_end <span class="sy2">-</span> time_beg</span></span> ）。若 <code>time_end</code> 代表先于 <code>time_beg</code> 的时间点，则结果为负。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>time_beg, time_end</td>
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<td>-</td>
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<td>待比较的时间</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>两时间之差的秒数。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>在 POSIX 系统上，<span class="t-lc"><a href="c-chrono-time_t.html">time_t</a></span> 以秒计量，而 <code>difftime</code> 等价于算术减法，但 C 和 C++ 允许小数单位的 <code>time_t</code> 。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<p>以下程序计算从月初开始经过的秒数。</p>
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="c source-c">
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<pre class="de1"><span class="co2">#include <stdio.h></span>
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<span class="co2">#include <time.h></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="c-chrono-time_t.html"><span class="kw523">time_t</span></a> now<span class="sy4">;</span>
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<a href="c-chrono-time.html"><span class="kw512">time</span></a><span class="br0">(</span><span class="sy3">&</span>now<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">struct</span> <a href="c-chrono-tm.html"><span class="kw522">tm</span></a> beg<span class="sy4">;</span>
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beg <span class="sy1">=</span> <span class="sy2">*</span><a href="c-chrono-localtime.html"><span class="kw519">localtime</span></a><span class="br0">(</span><span class="sy3">&</span>now<span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 设 beg 为月初</span>
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beg.<span class="me1">tm_hour</span> <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
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beg.<span class="me1">tm_min</span> <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
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beg.<span class="me1">tm_sec</span> <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span>
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beg.<span class="me1">tm_mday</span> <span class="sy1">=</span> <span class="nu0">1</span><span class="sy4">;</span>
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<span class="kw4">double</span> seconds <span class="sy1">=</span> difftime<span class="br0">(</span>now, <a href="c-chrono-mktime.html"><span class="kw520">mktime</span></a><span class="br0">(</span><span class="sy3">&</span>beg<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%.f seconds have passed since the beginning of the month.<span class="es1">\n</span>"</span>, seconds<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">return</span> <span class="nu0">0</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">1937968 seconds have passed since the beginning of the month.</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.27.2.2 The difftime function (p: 390)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.23.2.2 The difftime function (p: 339)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c89">
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<ul>
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<li>C89/C90 标准（ISO/IEC 9899:1990）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>4.12.2.2 The difftime function</li>
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</ul>
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</dd>
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</dl>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin"></table>
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</div>
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</div>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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